(SPACE.com) -- Until recently, black holes have remained hidden beneath invisibility cloaks. Whereas a lot has been known about the existence and properties of black holes from Einstein's theory of general relativity, tangible evidence has been a recent phenomenon.

Have astronomers gained wizard-like powers to view these regions in space that are so dense that nothing, not even light, can escape their gravitational pull? Not quite.

Rather, indirect evidence from X-ray telescopes has revealed telltale signs of thousands of black holes lurking in our own galaxy and beyond. Many are the remnants of exploded stars. But to other far more massive black holes, swallowing a single star is like Mount Everest absorbing a snowflake.

With their X-ray vision, and other techniques, researchers are monitoring the chaotic environments around these black holes trying to solve some longstanding mysteries.